The use of optics and optical devices in fields such as communications and computing has created a need for optical devices capable of performing information processing operations. This need extends to both digital and analog information processing operations.
The advent of symmetric self-electrooptic effect devices (SEEDs) has partially satisfied the need for optical information processing devices by enabling development of devices suitable for performing digital logic operations. Typical optical digital logic devices are switched based on the intensity of a pair of input signal beams, the ratio or difference of the intensities of the two beams representing an input data value. The first beam of the pair being more intense than the second represents a logic 0 value and the second beam being more intense than the first represents a logic 1 value. The intensities of the signal beams are selected to have sufficient contrast between a logic 0 value and a logic 1 value to ensure proper operation of the symmetric SEED and correct representation of the data.
The need for optical analog information processing devices, however, is largely unsatisfied. While an analog value is simplest to represent as a single light beam with a predetermined intensity, this representation causes problems in practical devices. One particularly troublesome problem is the difficulty in representing both positive and negative (bipolar) data values. This problem arises because the intensity of a light beam used to represent an analog datum can only be zero or positive; the light beam cannot have a negative intensity.